Field of the Invention
The present invention relates to a positioning device, a lithographic apparatus and a method for manufacturing a device.
Description of the Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. In order to ensure proper operation of the integrated circuit that is manufactured, an accurate positioning of the pattern relative to the substrate is required.
To provide in such accurate positioning, a positioning device including a so-called short-stroke module and a long-stroke module are often applied to position the substrate, e.g. relative to a reference frame such as a frame to which the projection system is mounted. Such a short-stroke module may e.g. comprise a plurality of actuators, e.g. electromagnetic actuators that enable a fine positioning of an object, e.g. an object table provided with a substrate, over comparatively small distances, e.g. less than or equal to a few mm. In order to displace the object table over larger distances, the short-stroke module may be mounted to a so-called long-stroke module which enables to displace the short-stroke module holding the object table over comparatively large distances, e.g. 500 mm or more. Such a long-stroke module may e.g. comprises a planar motor or a combination of multiple linear motors to displace the short stroke positioner in a substantially horizontal plane, e.g. below the projection system. In such arrangement, the long-stroke module is often displaceably mounted or supported onto a base frame of the apparatus, whereby a stator of the long-stroke module may e.g. be configured to operate as a balance mass when a reaction force is exerted on the stator, the reaction force being a reaction to a force generated on a mover of the long-stroke module. In such an arrangement, the mover of the long-stroke module is typically subjected to reaction forces originating from the short-stroke module that is mounted to it. Such reaction forces may cause an undesired vibration of the mover of the long-stroke module which may adversely affect the fine positioning of the object table by the short-stroke module. It would be desirable to provide in a long-stroke module in which the effects of such vibrations would be mitigated.